Stabilizers for photographic emulsions



Faientecl July 6, 1948 STABILIZERS FOR' PHOTOGRAPHIC EMULSIONS Newton Heimbach and Walter Kelly, Jix, Bing;

hamton, N. Y., assignors ,to -.Genera1 Aniline 8;, Film Corporation, New York, N. Y., a oorpo-- ration of Delaware Application December 15, 19515, Serial No. 35,335

11 Claims. 1

This invention relates to the, stabilization of light-sensitive silver-halide emulsions, and more particularly to the use of reaction products obtained by the condensation of a p-keto nitrile, or a ,s-imino nitrile, with a 3-amino-1,2,4.-triazole, as stabilizers for silver-halide emulsions.

It is known in the art that light-sensitive emulsions, such as gelatin silver-halide emulsions, have a decided tendency to fog. The fog may be of two types, namely, yellow fog and chemical (gray) fog. The yellow fog, sometimes referred to as color fog or dichroic fog, is essentiallyv a colloidal deposit of silver, the color intensity and general. appearance of which are determined by the minute particle size and degree of subdivision. The fog is chiefly yellow in color and is mostapparent in thelighter portions of a negative. The color may vary, however, and the colloidal silver particles may, for example, appear green by reflectedlight and yellow or red by transmitted light. The so-called chemical iog,,or gray fog, on the other hand, is the more common and is formed in a number of ways. It may be caused by premature exposure, by excessive ripening of the emulsions, or by the storage of the-film, particularly at high temperatures or for unusually long periods of time.

The primary object of the present invention is to provide stabilizers or fog inhibiting agents which tend to prevent the formation of chemical tained" by the condensation of a fl-ket'o nitrile, or a 18-iminonitrile, with a 3-amino-1,2,4-triazole.

The references in Beilstein have advanced the name hydroxy-1,3,4-triazaindolizines for the .re-

action product between a p-keto'ester and a :3-

"amino-l,2,4=triazole. Since a fi-imino nitrile or aB-keto nitrile is substituted for the B-keto ester in the same reaction to obtain the corresponding amino:l,3,4-triazaindolizines, the same terminol- .ogy will beemployed herein as in the Beilstein referencesto name the reaction products utilized .in accordance with our invention, and which products imply a craliformulaz structure of the. following, gen- L. l s R2 \N/ wherein R and R1 are either hydrogen, alkyl, e. g., methyl, ethyl, propyl, isopropyl, butyl, amyl, and the like, ,alicyclic, e. g., cyclopentyl, cyclohexyl, andthe like, aryl, e. g., phenyl, naphthyl, diphenyl, .etc., or arheterocyclic radical, e. g., pyridyl furyl, pyrryl, and the like, and R2 is either alkyl, alicyclic, aryl, or a heterocyclic radical of the same valueasR,

The method for the preparation of the hydroxy-1,3,4-triazaindolizines by condensing a p-keto ester with a 3-amino-1 ,2,4-triazole is given in Berichte 42, page 4643 and--4.3, pages 378-380. By substituting-ea peimino nitrile or a ,e-keto nitrile for. the fl-wketfl ester and employing the same reaction conditions ..described;ip these references, the amino-1,3,4-triazaindolizines utilized in accordance with this invention are readily prepared The 'method employed consists of heating 1 mol of a p-keto nitrile, or a ,B-imino nitrile, with 1 mol of a 3-amino-l,2,4-triazole of the following general formula:

wherein R is hydrogen, alkyl, e, g., methyl, ethyl, propyl, 'andwthe-like, or an ary-l'= radical, e, g., phenyl, naphthyl, diphenyl, and the like.

Suitable fl-keto nitriles are, for example, acetoacetonitrile, benzoyl acetonitrile, -ethyl acetoacetonitrile, a-phenyl acetoacetonitrile, and the like.

As examples of suitable p-imi-no nitriles' may be mentioned p-iminobutyronitrile, p-pyridylfl-iminopropionitrile, ,B-phenyl-p-iminopropionitrile, firtqlyl-er m nop cnionitnle nd, t like- As suitable 3-amino-1,2,4-triazoles 'may be mentioned, 3-amino-5-methyl-1,2,4-triazole, ,3;- amino-5-pheny1-1,2,4-triazole, 3-amino-1,2,4- .triazole, and the like.

The condensation between thep-keto nitrile, or a p-iminmnitrila -and the 3-amino-1,2,4-triazole, is carried outby heating the reaction components at a temperature ranging from C. to C'., preferably at reflux temperature in t p esence-oi.asuitablesolventsuchtas lacial acetic acid, pyridine, or alcoholic alkali (preferably in one of the latter two), for a period of three to eight hours. During this treatment, water and ammonia are formed. As the condensation or ring closure between the p-keto group ofthe'fl-ketonitrile, or the p-imino group of the ,B-imino nitrile, and the primary amino group of the 3-amino-l,2,4-triazole proceeds, the final product either precipitates or is removed by diluting the solvent with water, ethyl ether, ace-- tone. or the like.

I he p-keto nitriles, -imino nitriles, and the amino-1,2,4-triazoles are well-known to theart, and the method for their preparation need not be described herein.

Specific compounds which have been prepared according to the above procedure, with their probable formulae, are the following:

. l /OH 'I-amino-5-methyl-l,3,4-triazaindolizi.ne

4 7-amlno-5-phenyl-l,tA-triazsindolizine (a NH:

7:amino-5 methyl-2-phenyl-l,3,4-trla:aindoli2ine 1 7-aminofietIiyI-E-niethyl-l,3,4-trlazaindolizine =N CHrj v-ammutmeth l-c n n i-raem zaindent -N 7 amino-%riuryl-5-methyl-1,3,4-triazaindo1izine i l N 7-amino-5-fl-pyridyl-l,3,4-triazaindolizine IITHi HO N-N 7amino-2,E-dimethyl-l,3,4-triezalndolizine 7-amino-2-cyclohexylmethyl-l,3,4-ttiazaindolizine CHr-CH: l N/CH 7-amlno-5-cyclohexyl-l,3,4-triazaindolizine I 7-amino-5-methyl-6-cyclohexyl-l,3,4-triazaindolizine In the preparation of an emulsion containing the stabilizers used according to our invention, a solution of the stabilizer in a suitable solvent, such as alcoholor an alcohol-water mixture, ad: justed to a neutral or slightly alkaline pH, i. e.,

pH 7.5 to 10, is made up and the solution mixed with the emulsion at any point during its preparation, but preferably during ripening or just prior to coating in concentrations varying from 25 mg. to 500 mg. per liter of emulsion. The actual concentration employed will depend upon the type of emulsion used and variesslightly with the compound used.

The method of testing the stabilizers employed in the following examples consists of coating two film strips, such as cellulose acetate, with the same emulsion, one with and one without any stabilizer, storing the emulsions in an incubator for six days at 50 C., then exposing-developing,

Lfixiirlgfahd "fwash'irig the same juhdr standard #Qni f i e s ty o hingibr "ducedun tl ie "unxposedareas in tw'o' 'eniulsions is then measured in a transmission densitometer of standard type. v

The following examples will serve to illustrate certain ways in which thestabilizers of our invention have been applied, but "are not to be construed as limiting the invention.

Example I A photographic film coated with an ordinary gelatimbrom oiodide emulsion of normal speed --ai1d "contrast on development "under standard coiiditionsjia'fter incubation for six days "at; 0., gave a fog of 0.28 density. "'A'notherfilm coated with the same emulsion containing an addition of 100 mg. of compound 1 per 1000 cc. of emulsion equivalent to about grams of silver nitrate and developedfunder the same conditions, after the same incubation, gave a fog of only 0.08 density.

Example lI U a Teq uivalentqiiantity or eqnipdun was 'su ti H ted forcoiripo'u'n'd1,, The res'ults'obtained "were almosti dentical withthose obtained in Example I.

Erdmple III Example I was again repeated with the exception that 75' mg. of compound 3 were substituted for 100mg. of compound l After incubation and development, the emulsion containing com- H to the emulsion before or after thddyes are'added. The dispersing agents for the silver halide may. be gelatin or other colloid such as water-soluble cellulose derivatives 'e. 'g.,hydroxy ethyl cellulose, methyl cellulose, carboxy-oxy-cellulose, low ac'etyl value cellulose acetate and the like. The stabilizers may also be e nployed in gelatin or other colloid, such as polyainides or a mixture'of 'gelatin with'aifpolyl. ""amide as described'in United States'Patent r 289,775; polyvinyl alcohol and jelling compound as described in United States Patent 2,249,537; polyvinyl acetaldehyde acetal resins and partially hydrolyzed acetate resins described in United States Patents 1,939,422 and 2,036,092; cellulose derivatives, e. g., cellulose nitrate, cellulose acetate, the lower fatty acid esters of cellulose including simple and mixed esters, ethers of cellulose, and the like, as an under or overcoat for the emulsion, as as backing layer for the support. Moreover, they may be incorporated in the support for the sensitive emulsion layer or in an intermediate layer between the sensitive emulsion layer and the support, such as the baryta coating commonly used in photographic .E amplel w s r e te h the ex ption 5 ayemi l sion s if, used with sensitizing dyes- "paper *0; they ma t m'ctitqratqjin 1a T "tective layer coated lupon the' emuls'ion siir or the otherwise finished-photographic 8.1 may be bathed in e an alcohol or alcohol-waiter solution containing thestabilizer.

In the accompanying drawing the various figures are enlarged section views of photographic materials haw'ng anti iogging layers made accordin to our invention.

As showni'n Figure 1, the support I, which may be of any suitable{materialsuch as glass,

cellulose ester, synthetic resin, or" paper, is pro-' sensitive emulsion layer 2 'containing'asfiairantifogging layer such amino-'-1,3,4 triazaindolizines.

Since the presence of these new compounds tends to prevent chemical fog whether they are incorporated directly into the emulsion, added to a separate surfaceor substratum layer, it is understood that the term photographic material as employed herein and in the appended claims, is used in a generic sense to include each of these possible applications.

Various modifications of this invention" willoccur topersons skilled in the'artand it is, therefore, understood that the'patent giantedgshall only be limitedby the appended claims- We claim:

1. A'photograp'hic material comprising abase and a light-sensitive"silver-halide emulsion-carried thereby, said photographic material containing, in fog inhibiting amount, a compound ofthe general formula:

"whereini R andj Ri are members selectediifom the class consisting of hydrogen,'alkyl; alicyclic, aryl, and heterocyclic groups, and R2 is a member selected from the class consisting of alkyl, alicyclic, aryl, and heterocyclic radicals.

2. A photographic material comprising a base and a light-"sensitive silfver-halide emulsion carried thereby, saidphotographic material containing, in fog inhibiting amount, a compound of the following formula:

. 2,444,coo

3. A photographic material comprising a base and a light-sensitive silver-halide emulsion carried thereby, said photographic material con- Qtaining, in fog inhibiting amount, a compound of the following formula:

; v 4. A photographic material comprising a base and a light-sensitive silver-halide emulsion carried thereby, said photographic material containing, in fog inhibiting amount, a compound of the following formula:

I NH;

5. A photographic material comprising a base andra light-sensitive silver-halide emulsion containing, in fog inhibiting amount, a compound of the general formula:

wherein R and R1 are members selected from the class consisting of hydrogen, alkyl, alicyclio, aryl, and heterocyclic groups, and R2 is a member selected from the class consisting of alkyl, alicyclic, aryl, and heterocyclic radicals.

6.- A photographic material comprising a lightsensitive silver-halide emulsion containing, in fog inhibiting amount, a compound of the following i. formula:

CHs-l l N N '7. A photographic material comprising a lightsensitive silver-halide emulsion containing, in fog inhibiting amount, a compound of the following formula:

8 8. A photographic material comprising a lightsensitive silver-halide emulsion containing, in fog inhibiting amount, a compound of the following formula:

9. A photographic gelatino silver-halide emulsion containing from about 25 mg. to about 500 mg. per liter of emulsion of a compound of the following formula:

sion containing from about mg. to about 500 mg. per liter of emulsion of a compound of the following formula:

l1. Aphotographic gelatino silver-halide emulsiOn containing from about 25 mg. to about 500 mg. er liter of emulsion of a compound of the following formula:

NHz

NEWTON HEINIBACH. WALTER KELLY, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Heimbach Dec. 11, 1945 Number 2,390,707 

